Merge branch 'net-Ease-to-follow-an-interface-that-moves-to-another-netns'

Nicolas Dichtel says:

====================
net: Ease to follow an interface that moves to another netns

The goal of this series is to ease the user to follow an interface that
moves to another netns.

After this series, with a patched iproute2:

$ ip netns
bar
foo
$ ip monitor link &
$ ip link set dummy0 netns foo
Deleted 5: dummy0: <BROADCAST,NOARP> mtu 1500 qdisc noop state DOWN group default
    link/ether 6e:a7:82:35:96:46 brd ff:ff:ff:ff:ff:ff new-nsid 0 new-ifindex 6

=> new nsid: 0, new ifindex: 6 (was 5 in the previous netns)

$ ip link set eth1 netns bar
Deleted 3: eth1: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default
    link/ether 52:54:01:12:34:57 brd ff:ff:ff:ff:ff:ff new-nsid 1 new-ifindex 3

=> new nsid: 1, new ifindex: 3 (same ifindex)

$ ip netns
bar (id: 1)
foo (id: 0)
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/rtnetlink.h b/include/linux/rtnetlink.h
index 62d508b..0514cc3 100644
--- a/include/linux/rtnetlink.h
+++ b/include/linux/rtnetlink.h
@@ -19,10 +19,11 @@
 
 void rtmsg_ifinfo(int type, struct net_device *dev, unsigned change, gfp_t flags);
 void rtmsg_ifinfo_newnet(int type, struct net_device *dev, unsigned int change,
-			 gfp_t flags, int *new_nsid);
+			 gfp_t flags, int *new_nsid, int new_ifindex);
 struct sk_buff *rtmsg_ifinfo_build_skb(int type, struct net_device *dev,
 				       unsigned change, u32 event,
-				       gfp_t flags, int *new_nsid);
+				       gfp_t flags, int *new_nsid,
+				       int new_ifindex);
 void rtmsg_ifinfo_send(struct sk_buff *skb, struct net_device *dev,
 		       gfp_t flags);
 
diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
index 8616131..6d94477 100644
--- a/include/uapi/linux/if_link.h
+++ b/include/uapi/linux/if_link.h
@@ -163,6 +163,7 @@
 	IFLA_IF_NETNSID,
 	IFLA_CARRIER_UP_COUNT,
 	IFLA_CARRIER_DOWN_COUNT,
+	IFLA_NEW_IFINDEX,
 	__IFLA_MAX
 };
 
diff --git a/net/core/dev.c b/net/core/dev.c
index 4670cca..858501b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7360,7 +7360,7 @@
 		if (!dev->rtnl_link_ops ||
 		    dev->rtnl_link_state == RTNL_LINK_INITIALIZED)
 			skb = rtmsg_ifinfo_build_skb(RTM_DELLINK, dev, ~0U, 0,
-						     GFP_KERNEL, NULL);
+						     GFP_KERNEL, NULL, 0);
 
 		/*
 		 *	Flush the unicast and multicast chains
@@ -8473,7 +8473,7 @@
 
 int dev_change_net_namespace(struct net_device *dev, struct net *net, const char *pat)
 {
-	int err, new_nsid;
+	int err, new_nsid, new_ifindex;
 
 	ASSERT_RTNL();
 
@@ -8529,11 +8529,16 @@
 	call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
 	rcu_barrier();
 	call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);
-	if (dev->rtnl_link_ops && dev->rtnl_link_ops->get_link_net)
-		new_nsid = peernet2id_alloc(dev_net(dev), net);
+
+	new_nsid = peernet2id_alloc(dev_net(dev), net);
+	/* If there is an ifindex conflict assign a new one */
+	if (__dev_get_by_index(net, dev->ifindex))
+		new_ifindex = dev_new_index(net);
 	else
-		new_nsid = peernet2id(dev_net(dev), net);
-	rtmsg_ifinfo_newnet(RTM_DELLINK, dev, ~0U, GFP_KERNEL, &new_nsid);
+		new_ifindex = dev->ifindex;
+
+	rtmsg_ifinfo_newnet(RTM_DELLINK, dev, ~0U, GFP_KERNEL, &new_nsid,
+			    new_ifindex);
 
 	/*
 	 *	Flush the unicast and multicast chains
@@ -8547,10 +8552,7 @@
 
 	/* Actually switch the network namespace */
 	dev_net_set(dev, net);
-
-	/* If there is an ifindex conflict assign a new one */
-	if (__dev_get_by_index(net, dev->ifindex))
-		dev->ifindex = dev_new_index(net);
+	dev->ifindex = new_ifindex;
 
 	/* Send a netdev-add uevent to the new namespace */
 	kobject_uevent(&dev->dev.kobj, KOBJ_ADD);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index f111557..e04af7b 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -988,6 +988,7 @@
 	       + rtnl_xdp_size() /* IFLA_XDP */
 	       + nla_total_size(4)  /* IFLA_EVENT */
 	       + nla_total_size(4)  /* IFLA_NEW_NETNSID */
+	       + nla_total_size(4)  /* IFLA_NEW_IFINDEX */
 	       + nla_total_size(1)  /* IFLA_PROTO_DOWN */
 	       + nla_total_size(4)  /* IFLA_IF_NETNSID */
 	       + nla_total_size(4)  /* IFLA_CARRIER_UP_COUNT */
@@ -1511,7 +1512,8 @@
 			    struct net_device *dev, struct net *src_net,
 			    int type, u32 pid, u32 seq, u32 change,
 			    unsigned int flags, u32 ext_filter_mask,
-			    u32 event, int *new_nsid, int tgt_netnsid)
+			    u32 event, int *new_nsid, int new_ifindex,
+			    int tgt_netnsid)
 {
 	struct ifinfomsg *ifm;
 	struct nlmsghdr *nlh;
@@ -1608,6 +1610,10 @@
 	if (new_nsid &&
 	    nla_put_s32(skb, IFLA_NEW_NETNSID, *new_nsid) < 0)
 		goto nla_put_failure;
+	if (new_ifindex &&
+	    nla_put_s32(skb, IFLA_NEW_IFINDEX, new_ifindex) < 0)
+		goto nla_put_failure;
+
 
 	rcu_read_lock();
 	if (rtnl_fill_link_af(skb, dev, ext_filter_mask))
@@ -1853,7 +1859,7 @@
 					       NETLINK_CB(cb->skb).portid,
 					       cb->nlh->nlmsg_seq, 0,
 					       flags,
-					       ext_filter_mask, 0, NULL,
+					       ext_filter_mask, 0, NULL, 0,
 					       netnsid);
 
 			if (err < 0) {
@@ -3088,7 +3094,7 @@
 	err = rtnl_fill_ifinfo(nskb, dev, net,
 			       RTM_NEWLINK, NETLINK_CB(skb).portid,
 			       nlh->nlmsg_seq, 0, 0, ext_filter_mask,
-			       0, NULL, netnsid);
+			       0, NULL, 0, netnsid);
 	if (err < 0) {
 		/* -EMSGSIZE implies BUG in if_nlmsg_size */
 		WARN_ON(err == -EMSGSIZE);
@@ -3184,7 +3190,8 @@
 
 struct sk_buff *rtmsg_ifinfo_build_skb(int type, struct net_device *dev,
 				       unsigned int change,
-				       u32 event, gfp_t flags, int *new_nsid)
+				       u32 event, gfp_t flags, int *new_nsid,
+				       int new_ifindex)
 {
 	struct net *net = dev_net(dev);
 	struct sk_buff *skb;
@@ -3197,7 +3204,7 @@
 
 	err = rtnl_fill_ifinfo(skb, dev, dev_net(dev),
 			       type, 0, 0, change, 0, 0, event,
-			       new_nsid, -1);
+			       new_nsid, new_ifindex, -1);
 	if (err < 0) {
 		/* -EMSGSIZE implies BUG in if_nlmsg_size() */
 		WARN_ON(err == -EMSGSIZE);
@@ -3220,14 +3227,15 @@
 
 static void rtmsg_ifinfo_event(int type, struct net_device *dev,
 			       unsigned int change, u32 event,
-			       gfp_t flags, int *new_nsid)
+			       gfp_t flags, int *new_nsid, int new_ifindex)
 {
 	struct sk_buff *skb;
 
 	if (dev->reg_state != NETREG_REGISTERED)
 		return;
 
-	skb = rtmsg_ifinfo_build_skb(type, dev, change, event, flags, new_nsid);
+	skb = rtmsg_ifinfo_build_skb(type, dev, change, event, flags, new_nsid,
+				     new_ifindex);
 	if (skb)
 		rtmsg_ifinfo_send(skb, dev, flags);
 }
@@ -3235,14 +3243,15 @@
 void rtmsg_ifinfo(int type, struct net_device *dev, unsigned int change,
 		  gfp_t flags)
 {
-	rtmsg_ifinfo_event(type, dev, change, rtnl_get_event(0), flags, NULL);
+	rtmsg_ifinfo_event(type, dev, change, rtnl_get_event(0), flags,
+			   NULL, 0);
 }
 
 void rtmsg_ifinfo_newnet(int type, struct net_device *dev, unsigned int change,
-			 gfp_t flags, int *new_nsid)
+			 gfp_t flags, int *new_nsid, int new_ifindex)
 {
 	rtmsg_ifinfo_event(type, dev, change, rtnl_get_event(0), flags,
-			   new_nsid);
+			   new_nsid, new_ifindex);
 }
 
 static int nlmsg_populate_fdb_fill(struct sk_buff *skb,
@@ -4642,7 +4651,7 @@
 	case NETDEV_CHANGELOWERSTATE:
 	case NETDEV_CHANGE_TX_QUEUE_LEN:
 		rtmsg_ifinfo_event(RTM_NEWLINK, dev, 0, rtnl_get_event(event),
-				   GFP_KERNEL, NULL);
+				   GFP_KERNEL, NULL, 0);
 		break;
 	default:
 		break;